The field of the invention is in the area of transgenic mice, specifically, a transgenic mouse lacking the mitochondrial protein called heart-muscle adenine nucleotide translocator, and in the testing of genetic therapies and/or pharmaceuticals in animal model systems, particularly those genetic therapies and/or pharmaceuticals of benefit in protecting against or ameliorating mitochondrial myopathy and/or certain mitochondrial disease in a human or animal susceptible to or suffering from same.
Mitochondrial oxidative phosphorylation (OXPHOS) is a complex biochemical process central to aerobic energy metabolism. Oxidative energy (in the form of electrons donated by NADH or FADH.sub.2) is transformed by the electron transport chain (Complexes I-IV) into a chemiosmotic gradient across the inner mitochondrial membrane that is utilized by ATP synthase (Complex V) to phosphorylate ADP, providing ATP as an energy source for the cell.
Heart-muscle adenine nucleotide translocator, encoded by the ANT1 locus, is the most abundant mitochondrial protein. ANT1 is encoded by a nuclear gene, and the functional unit is a 60 kDa homodimer embedded in the inner mitochondrial membrane. ANT plays a central role in OXPHOS by acting as a solute carrier which imports ADP from the cytosol into the mitochondrial matrix (to be phosphorylated by ATP synthase) and exports newly phosphorylated ATP from the matrix into the cytosol. Thus, it plays a critical role in energy metabolism. ANT exists in multiple isoforms in many species. In mammals, these ANT isoforms exhibit tissue-specific gene expression patterns (Stepien et al. (1992) J. Biol. Chem. 267:14592-14597 and hereinbelow). Ant1 is considered a heart/muscle specific isoform due to its predominant expression in cardiac and skeletal muscle.
Studies over the past 10 years linking mutations in mitochondrial DNA and human disease have supported a mitochondrial OXPHOS paradigm that hypothesizes defects in OXPHOS result in disease manifesting itself in tissues most dependent on oxidative metabolism (i.e., CNS, heart, skeletal muscle) [reviewed in Wallace, D.C. (1994) J. Bioenerg. Biomem. 26:241-250; Brown, M.D. and Wallace, D.C. (1994) J. Bioenerg. Biomem. 26:273-289]. A defect in ANT1 in three different facioscapulohumeral muscular dystrophy patients has been suggested by Wijmenga et al. (1993) Hum. Genet. 92:198-203.
In order to directly test this paradigm and to better understand the biological role of multiple ANT isoforms, the present inventors have made "knockout" mice lacking a functional Ant1 gene product.
Oxygen radical injury has been implicated in pulmonary oxygen toxicity, adult respiratory distress syndrome, bronchopulmonary dysplasia, sepsis syndrome and various ischemia-reperfusion syndromes including myocardial infarction, stroke, cardiopulmonary bypass, organ transplantation, necrotizing enterocolitis, acute renal tubular necrosis, among others. Oxygen radical damage can result from a disruption of mitochondrial energy generation, for example, when normal ATP/ADP exchange is blocked. Accumulated free radical damage has also been associated with the normal aging process.